Electric burglar-alarm.



B. BECK.

ELECTRIC BURGLAB ALARM. APPLICATION FILED MAR. 9. l9l8.

PatentedNov. 26, 1918..

BERNI-IARDT BECK, 0]? OUT BANK, MONTANA.

ELECTRIC BURGLAR-ALARM.

Specification of Letters Patent.

Patented Nov. 26, 1918.

Application filed March 9, 1918. Serial No. 221,379.

To all whom it may concern:

Be it known that I, BERNHARDT BECK, a subject of the Emperor of Germany,resident of Cut Bank, county of Teton, and State of Montana, haveinvented certain new and useful Improvements in Electric Burglar-Alarms,of which the following is a specification.

This invention relates to improvements in burglar alarms andparticularly to types adapted to be engaged with the doors of a buildingin which it is desirable to give an audible signal whenever the door isunlocked.

The principal object of the invention is to provide an apparatus whichwill cause a signal to be given whenever. a key is inserted in the doorlook.

A further object is to provide such device which may be permanentlyengaged with one side of the door lock, the apparatus being in sectionsone of which is readily removable so as to present no disfigurement orobjectionable appearance.

These and other like objects are attained by the novel construction andcombination of parts hereinafter described and shown in the accompanyingdrawing, forming a material part of this disclosure, and in which:

Figure 1 is a fragmental edge view of a conventional form of door,containing an ordinary lock and operating knobs and indicating theapplication of the invention.

Fig. 2 is a vertical sectional view taken through the center of thekey-hole and indicating the operation of the device.

Fig. 3 is a fra-gmental side elevational view of the same, and

Fig. 4 is a vertical sectional view taken on line H of Fig. 2.

Throughout the several figures the numeral 10 designates a door ofconventional type, containing a lock-casing 11, through which extends alock bolt 12, engageable with a keeper formed in the frame of the door(not shown), and a latch 13, operated by the knobs 14, all of theforegoing parts being of the usual type of construction.

Secured to the inner side of the door 10, so as to cover one of thekey-openings 16, is a fiat plate 17, the same having angularly disposedelements 18, upon opposite ends, terminating in flanges 19, securedpermanently by screws 20, to the side of the door, and containing anelongated vertical slot 22, formed centrally through the plate 17,through which may be passed a rectangular plate 23, secured to the lowerend of a tubular screw 25, passing freely through the slot 22, and awooden block 26, which has a counterbored opening 27, in its outersurface, containing the lower end of a helically coiled compressionspring 28, the outer end of which abuts against a washer 29, and iscompressed by operating a knurled nut 30, the purpose of the same beingto clamp the plate 23, when arranged transversely across the slot 22,against the inner side of the plate 17, so as to hold the block 26 inengagement.

Passing centrally through the bore of the tubular screw 25, is a rod 32,adapted to enter the key-hole l6, and register with the stern of anentered key 35, there being secured to the rod 32, a fixed collar 33,which, when the rod is extended as far outward as is possible, will makecontact with the plate 23.

The outer extending end of the rod 32, is screw threaded and has securedto it a conical metallic sleeve 36, adjoining which is a thimble 37,having secured to its outer end a knob 38, made of non-conductingmaterial, and having an inner extending stem 39 of cylindrical shapeadapted to engage with the curved ends 40, of a pair of opposed flatsprings 42, secured to the wooden insulating block 26, by binding screws43, which engage wires 44 and 45, respectively, which lead from a sourceof electricity, as an ordinary primary cell battery (not shown) and incircuit with which is an electric bell.

In operation, the plate 17, is permanently secured to the inner side ofthe door, the slot 22 in the plate alining with the key hole, so as topermit the lock to be operated in the ordinary manner.

When it is desired to attach the alarm, the block 26, is secured inposition by pressing the knob 30 inward, so as to allow the plate 23 toenter and pass through the slot 22, whereupon releasing the knob, thespring clamps the block firmly in engagement with the outer surface ofthe plate 17. Theknob 38 is pressed in to its full extent, causing thesprings 42, to slide over the cone 36, and over the rounded edges of theintermediate thimble 37, resting upon the cylindrical surface-39 of theknob 88, holding the rod 32, in an inward position, as best shown inFig. 1, so that when contact is made at the extreme end of the rod 32 bythe entrance of the key 35, the rod 32 will be pushed out, carrying theknob with it and allowing the springs e2 to make contact with the cone36, which completes the circuit, causing an alarm by reason of theelectric bell, giving audible notification that a key has been enteredin the lock. Obsviously, when the springs e2 areheld apart by the knobstem 39, the circuit is broken and no current is conveyed to the alarm.

From the foregoing it will be seen that when the attachment is not inuse it can be readily removed by pressing the knob 38 toward the door,rotating the block and removing the same together with its attachments.

Having thus described my invention what I claim as-new and desire tosecurevby Letters Patent, is

In a burglar alarm, in combination, a door, a lock engaged therewith, arigid plate supported by said door, a block engageable therewith, meansfor clamping said block to said plate, a. tubular screw slidable in saidblock, a spring operating to move said screw within said block, meansfor adjusting the tension of said spring, a rod slidably engaged insaid. tubular screw, a pair of contact arms arranged upon opposite sidesof said block, an insulated knob formed at. the extreme end of said.rod, anda conicalengaging element adjacent to said knob, whereby whensaidrod is'pressed outwardly said contact arms areplaced in .circuit.

In testimony whereof I have uaflixed my signature.

:BERNHARDT' BECK.

Copies of this patentvmay be obtainedfor five cents each, by addressingthe Commissioner of Patents, Washington. I). 0.

